It is the largest expanse of blanket bog in Europe, and covers about 4,000 square kilometres (1500 mile²). Blanket bogs are wet peat formations that sit in depressions and grow at a very slow rate, usually about 1mm a year. Sphagnum mosses create and sustain the bogs. Other plants can be found in ridges, hummocks and in small pools.

The Flow Country was badly damaged between 1979 and 1987 through the planting of non-native conifer forests and the cutting of thousands of miles of drains. The trees dried out the peat, changing the habitat and destroying its value for birds and other wildlife. The trees were mostly planted on land bought by Fountain Forestry who recognised that this would be attractive to wealthy investors who could claim planting grants and tax relief against all their other income, at a time of high personal taxation. The ploughing of the bogs and tree planting helped to reduce local unemployment which was among the highest in the United Kingdom: however in 1987 the Nature Conservancy Council (NCC) launched a report in London that was highly critical of the foresters. The Scots angered by this interference in Scottish affairs persuaded the Conservative Party Government to disband the NCC and create a separate Scottish Agency now called Scottish Natural Heritage. However in 1988 Nigel Lawson, recognised that a tax break for wealthy investors including, amongst others, Terry Wogan, Cliff Richard and Phil Collins, was doing enormous harm to the last real wilderness in the United Kingdom and scrapped the forestry tax reliefs. This immediately halted further planting and encouraged the Forestry Commission to adopt a much broader approach that respects existing landscapes. In an effort to restore the damage, the Royal Society for the Protection of Birds (RSPB) have bought a large area in the centre of the Flow Country and have created the Forsinardnature reserve. More than 20 km² has been bought back from Fountain Forestry and the young trees felled and allowed to rot in the plough furrow in the hope and expectation that, in 30-100 years, the land will revert to peat bog.